Spoilers have been used on the rear end of vehicles for many years and in search of the records the patent to Schumaker U.S. Pat. No. 3,089,728 was found which is a unit designed to block the flow of water over the rear window of an automobile and to utilize at least a portion of the air flow to assist in washing this water across the rear window. Applicant's device is not designed to wash any rear windows but merely and solely to deflect the air flow from across the top of the vehicle to a direction vertical of the truck body, thus preventing a vacuum forming in the rear of the vehicle. Also was found patent to Heck U.S. Pat. No. 3,960,402 which consists of a series of vanes so mounted and so arranged to direct the flow of air from the top and sides of the vehicle to a point in the rear of the vehicle to avoid the formation of a vacuum. Applicant's device does not direct the air to a point to the rear of the vehicle but on the contrary directs it downwardly across the back end of the vehicle body.